Timer that invokes a Cloud Functions function

Timer is a trigger that calls a Cloud Functions function on a schedule. The schedule is set as a cron expression. The cron expression uses UTC+0.

A timer needs a service account to invoke a function.

For more information about creating a timer, see Creating a timer that invokes a Cloud Functions function.

Cron expression formatCron expression format

The order of fields in the cron expression: Minutes Hours Day-of-month Month Day-of-week Year.

Possible field valuesPossible field values

Special charactersSpecial characters

You can use the following special characters in cron expressions:

• *: Select all values in the field.

  The * character in the Minutes field: The trigger starts every minute.

• ?: Select any field value. You can't fill Day of month and Day of week at the same time. If you entered a value in one of these fields, enter ? in the other field.

  10 in Day of month and ? in Day of week: The trigger is launched every 10th day of the month.

• -: Select a range of values.

  The 10-12 range in Hours: the trigger runs at 10 AM, 11 AM, and noon.

• ,: Select multiple values.

  MON,WED,FRI in the Day of week field: the trigger runs on Monday, Wednesday, and Friday.

• /: Increment the value.

  0/15 in the Minutes field: The trigger starts at 0, 15, 30, and 45 minutes past each hour.

• L: This character functions differently in the two fields where it's used:

  • In the Day of month field, it means the last day of the month.
  • In the Day of week field, it means the last day of the week, 7 (Saturday, SAT).

  L in the Day of month field: the trigger runs on January 31, February 28, and so on.

• W: Select the weekday nearest to the specified date.

  15W in the Day of month field: The trigger is run on the weekday nearest to the 15th day of the month. If the 15th day is Saturday, the trigger runs on Friday the 14th.

  Note

  The characters L and W in the Day of month field can be also merged into LW: The trigger is run on the last weekday of the month.

• #: Select the Nth day of the month.

  The value 6#3 in the Day of week field: The trigger runs on the third Friday of the month (6 — Friday, 3 — the third Friday of the month).

Examples of cron expressionsExamples of cron expressions

Roles required for timers to run correctlyRoles required for timers to run correctly

• To create a timer, you need a permission for the service account under which the timer runs the operation. This permission comes with the iam.serviceAccounts.user and editor roles or higher.
• To run a timer, the service account needs the functions.functionInvoker role for the folder containing the function called by the timer.

Read more about access management.

Timer message formatTimer message format

After the trigger is activated, it sends the following message to the function:

{
  "messages": [
    {
      "event_metadata": {
        "event_id": "a1s41g2n5g0o********",
        "event_type": "yandex.cloud.events.serverless.triggers.TimerMessage",
        "created_at": "2019-12-04T12:05:14.227761Z",
        "cloud_id": "b1gvlrnlei4l********",
        "folder_id": "b1g88tflru0e********"
      },
      "details": {
        "trigger_id": "a1sfe084v4se********",
        "payload": "payload-message"
      }
    }
  ]
}

Use casesUse cases

• Yandex Tracker: data export and visualization
• Status monitoring of geographically distributed devices
• Scheduled scaling of instance groups using the management console, CLI, and API
• Sensor reading monitoring and event notifications
• Deploying a fault-tolerant architecture with preemptible VMs
• Running computations on a schedule in DataSphere

See alsoSee also

• Timer to run a Serverless Containers container
• Timer that sends messages to WebSocket connections